U.S. patent application number 15/969849 was filed with the patent office on 2019-11-07 for maintenance of a steam bubble during surgical ablation.
This patent application is currently assigned to InnovaQuartz LLC. The applicant listed for this patent is InnovaQuartz LLC. Invention is credited to Stephen E. Griffin.
Application Number | 20190336216 15/969849 |
Document ID | / |
Family ID | 68383601 |
Filed Date | 2019-11-07 |
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United States Patent
Application |
20190336216 |
Kind Code |
A1 |
Griffin; Stephen E. |
November 7, 2019 |
Maintenance of a Steam Bubble During Surgical Ablation
Abstract
A surgical method and tool for establishing a steam bubble
between a fiber tip and a surgical target. The device and process
capable of maintaining the steam bubble by providing a low-power,
continuous-wave laser emission. Furthermore, the method and tool
capable of delivering to the surgical target through the steam
bubble a therapeutic laser emission providing ablation of the
surgical target.
Inventors: |
Griffin; Stephen E.;
(Peoria, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
InnovaQuartz LLC |
Phoenix |
AZ |
US |
|
|
Assignee: |
InnovaQuartz LLC
Phoenix
AZ
|
Family ID: |
68383601 |
Appl. No.: |
15/969849 |
Filed: |
May 3, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 2018/2222 20130101;
A61B 2018/00577 20130101; A61B 2018/263 20130101; G02B 6/262
20130101; A61B 18/22 20130101; A61B 18/26 20130101; G02B 6/02047
20130101; G02B 6/4296 20130101; G02B 6/02033 20130101; A61B
2018/206 20130101 |
International
Class: |
A61B 18/22 20060101
A61B018/22 |
Claims
1. A surgical method comprising: establishing a steam bubble
between a fiber tip and a surgical target; maintaining the steam
bubble by providing a low-power, continuous-wave laser emission;
and then delivering to the surgical target through the steam bubble
a therapeutic laser emission; wherein the therapeutic laser
emission provides the ablation of the surgical target.
2. The surgical method of claim 1, wherein the continuous-wave
laser emission has a divergent emission from the fiber tip.
3. The surgical method of claim 1, wherein the continuous-wave
laser emission has an annular beam profile.
4. The surgical method of claim 1, wherein the continuous-wave
laser emission has an emissions wavelength of 1930.+-.30 nm and a
power output of less than 5 Watts.
5. The surgical method of claim 1, wherein the therapeutic laser
emission has a wavelength greater than 1960 nm and a power output
of greater than 10 Watts.
6. The surgical method of claim 1, wherein the therapeutic laser
emission has a wavelength less than 500 nm.
7. The surgical method of claim 1, wherein the continuous-wave
laser emission and the therapeutic laser emission are provided via
an optical fiber having a fused silica core, the fused silica core
clad with a fluorine doped silica cladding, the fluorine doped
silica cladding having a polymer cladding; wherein the therapeutic
laser emission is contained within the fused silica core by the
fluorine doped silica cladding.
8. The surgical method of claim 7, further comprising providing the
continuous-wave laser emission to the optical fiber with a
high-angle launch of greater than about 4.degree. off the fiber
longitudinal axis.
9. The surgical method of claim 1, wherein establishing the steam
bubble includes providing the continuous-wave laser emission and/or
the therapeutic laser emission to water positioned between the
fiber tip and the surgical target.
10. The surgical method of claim 9, wherein the continuous-wave
laser emission has an annular beam profile, and wherein the steam
bubble is established by therapeutic laser emission.
11. The surgical method of claim 1, wherein a volume of the steam
bubble changes less than 50 vol. % while delivering the therapeutic
laser emission to the surgical target.
12. The surgical method of claim 1, wherein the method provides a
single steam bubble.
13. The surgical method of claim 1, wherein the steam bubble is
adjacent to the surgical target.
14. The surgical method of claim 1, wherein maintaining the steam
bubble reduces retropulsion.
15. The surgical method of claim 1, wherein the therapeutic laser
emission has a power output of greater than 10 Watts at the fiber
tip; and wherein maintaining the steam bubble prevents a reduction
of the power output between the fiber tip and the surgical
target.
16. A surgical device comprising: a therapeutic laser emission
source having a power output of greater than 10 Watts; a
continuous-wave laser emission source having a power output of less
than 5 Watts; a low angle therapeutic laser emission launch adapted
to provide a therapeutic laser emission to a core of an optical
fiber; and a high angle continuous-wave laser emission launch
adapted to provide a continuous-wave laser emission to the optical
fiber with a launch angle of greater than about 4.degree.; wherein
the low-angle and high-angle of the respective launches are with
respect to a longitudinal axis of the optical fiber.
17. The surgical device of claim 16 further comprising the optical
fiber having a fused silica core, the fused silica core clad with a
fluorine doped silica cladding, the fluorine doped silica cladding
having a polymer cladding.
18. The surgical device of claim 16, wherein the therapeutic laser
emission source is a holmium laser or a thulium laser.
19. The surgical device of claim 16, wherein the continuous-wave
laser emission source is one or more laser diodes or diode-pumped
solid-state lasers, the emission source having an emissions
wavelength of 1930.+-.30 nm.
20. The surgical device of claim 17, wherein the high angle
continuous-wave laser emission launch adapted to provide a
continuous-wave laser emission to the optical fiber with a launch
angle of greater than about 4.degree., wherein the launch and
launch angle are adapted carry the continuous-wave laser emission
in the fluorine doped silica cladding.
Description
FIELD OF THE INVENTION
[0001] Embodiments of the present invention generally relate to
laser energy generators intended for fragmenting or ablating
urinary, biliary and salivary calculi and vaporization, excision,
incision, ablation and coagulation of soft tissues using infrared
wavelengths.
BACKGROUND
[0002] Absorption of laser energy by water is the basis of laser to
tissue interaction of infrared lasers such as holmium (2080 nm to
2140 nm) and thulium (1900 nm to 2000 nm) FIG. 1. Within
endosurgical techniques, surgical fields are also water based (e.g.
saline or ringers). Laser energy is absorbed strongly within any
gap between the laser fiber exit aperture and the tissue. In pulsed
laser techniques, the first portion of each laser pulse is spent in
boiling water, producing a steam bubble referred to as a "Moses
bubble" in the field of art. Where pulse energies are low, e.g. 0.2
joules, and the fiber tip to target distance is considerable, e.g.
1 mm, most or all of the laser energy may be consumed in simply
boiling water.
[0003] Prior art has addressed this issue for pulsed lasers by
providing closely spaced or overlapping pulses: a small pulse to
produce a vapor bubble though which a second, larger pulse may pass
with minimal interaction with the surgical irrigant. As taught by
U.S. Pat. No. 5,321,715, laser energy traveling in a liquid medium
toward a target tissue will be absorbed, but that absorption may be
less than expected due to the "Moses Effect". As in the Biblical
reference, the waters are parted by a first component of the pulse
energy in producing a vapor bubble (Moses bubble) within the liquid
medium. The remaining pulse energy passes through the far less
attenuating medium of the bubble, resulting in higher that
initially anticipated coupling of energy to the target.
[0004] The '715 patent describes a pulse format to increase the
amount of laser energy which will arrive at the target tissue.
According to the description, a first short and low energy
initiation pulse is generated in order to create a bubble, followed
by a higher energy treatment pulse. The second (treatment) pulse,
when it passes through the created and now-formed bubble,
experiences a lower absorption rate due to the presence of the
bubble (and the absence of liquid). Moreover, the '715 patent
teaches that the energy of the first bubble initiation pulse be
sufficient enough to initiate the formation of a vapor bubble. The
bubble thus formed may then displace a substantial portion of the
fluid medium between a tip of a laser fiber and a target
tissue.
[0005] Additional prior art has concentrated upon optimization of
the Moses Effect. U.S. Pat. No. 5,632,739 teaches that a delay
between a bubble initiation pulse and a treatment pulse is chosen
so that the second pulse is emitted when the bubble size and
corresponding amount of displaced fluid is at its maximum extent.
U.S. Pat. No. 9,895,196 teaches optimization of reduced
retropulsion (movement of target calculus away from the laser pulse
source) in alternative timing of laser pulses.
[0006] Retropulsion is a is a phenomenon that is highly variable in
real-world surgery and appears to be a function of laser pulse
energy and repetition rate as well as fiber tip to target distance,
stone composition and stone location in the anatomical region. In
timing the second laser pulse for delivery just as the bubble
begins to collapse, the '196 patent teaches the stone will be drawn
in to the beam at the same time it is repulsed by the second pulse,
maintaining the stone at a fixed distance from the fiber, where the
separation of fiber and target is critical to the optimization of
energy coupling efficiency.
[0007] U.S. Pat. No. 6,998,567 teaches the production of a
multi-pulse train primarily for improved energy efficiency in
generating the laser pulses, but with a mention of overlapping
pulses for enhancing acoustic and thermal effects upon the
target.
SUMMARY
[0008] In accordance with aspects of the present invention, a dual
wavelength, dual mode surgical laser is provided. The system is
comprised of a standard "holmium" surgical laser generating pulses
of energy for ablation or fragmentation of biological calculi or
tissue, the output energy of which is overlaid on a continuous wave
(CW) laser output at or very near the 1930 nm absorption maximum
for water.
[0009] A first embodiment is a surgical method that includes
establishing a steam bubble between a fiber tip and a surgical
target; maintaining the steam bubble by providing a low-power,
continuous-wave laser emission; and then delivering to the surgical
target through the steam bubble a therapeutic laser emission
providing ablation of the surgical target.
[0010] A second embodiment is a surgical device that includes a
therapeutic laser emission source having a power output of greater
than 10 Watts, 25 Watts, 50 Watts, or 100 Watts; a continuous-wave
laser emission source having a power output of less than 5 Watts,
less than 2 Watts, less than 1 Watt, less than 0.5 Watts, or less
than 0.2 Watts; a low angle therapeutic laser emission launch
adapted to provide a therapeutic laser emission to a core of an
optical fiber; a high angle continuous-wave laser emission launch
adapted to provide a continuous-wave laser emission to the optical
fiber with a launch angle of greater than about 4.degree.,
8.degree., 12.degree., or 15.degree.; wherein the low-angle and
high-angle of the respective launches are with respect to a
longitudinal axis of the optical fiber.
BRIEF DESCRIPTION OF THE FIGURES
[0011] For a more complete understanding of the disclosure,
reference should be made to the following detailed description and
accompanying drawing figures wherein:
[0012] FIG. 1 is a graph of infrared light absorption in water;
[0013] FIG. 2 is an isometric representation of a typical laser
lithotripsy fiber construction with divergent output (FIG. 2A) and
detail of the input end (FIG. 2B);
[0014] FIG. 3 depicts the attenuation/transmission spectra for the
primary NA (AFS fiber) and secondary NA (HPC fiber) for fiber of
the type used in laser lithotripsy surgery;
[0015] FIG. 4 shows three surgical fiber output beam profiles
relevant to the invention; and
[0016] FIG. 5 illustrates an off-axis launch of a continuous-wave
laser emission into a fiber with a pulsed therapeutic laser, and
the output beams.
[0017] While specific embodiments are illustrated in the figures,
with the understanding that the disclosure is intended to be
illustrative, these embodiments are not intended to limit the
invention described and illustrated herein.
DETAILED DESCRIPTION
[0018] Objects, features, and advantages of the present invention
will become apparent from the following detailed description. It
should be understood, however, that the detailed description and
the specific examples, while indicating specific embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
[0019] Herein, the use of the word "a" or "an" when used in
conjunction with the term "comprising" in the claims and/or the
specification may mean "one," but it is also consistent with the
meaning of "one or more," "at least one," and "one or more than
one." The term "about" means, in general, the stated value plus or
minus 5%. The use of the term "or" in the claims is used to mean
"and/or" unless explicitly indicated to refer to alternatives only
or the alternative are mutually exclusive, although the disclosure
supports a definition that refers to only alternatives and
"and/or."
[0020] Herein are provided components for and an improved surgical
laser system for coupling infrared surgical energy to biological
targets within a water-based medium.
[0021] FIG. 1 depicts the absorption spectrum of water within the
wavelength range of interest to this invention, where 10 represents
the peak absorption at approximately 1930 nm, 20 represents the
absorption at the nominal wavelength for broadly used "thulium"
lasers, and 30 represents the absorption at the nominal wavelength
for common "holmium" lasers. For reference, it should be noted that
holmium lasers produce a pulsed output, typically ranging from 0.2
Joules (J) per pulse to 6 J per pulse at a repetition rate ranging
from 5 Hertz (Hz) to 60 Hz and average power ranging from
approximately 12 Watts (W) to 120 W, maximum, where thulium lasers
are typically continuous output lasers (continuous wave, or CW)
with average powers of 100 W to 250 W. The laser energy is
generally coupled to an optical fiber for delivery to the surgical
target within the body.
[0022] Where pulse energies are low, e.g. 0.2 joules per pulse, and
the distance between the optical fiber output tip and kidney stone
is large, e.g. 1 mm or greater, essentially none of the surgical
energy arrives at the stone. Where pulse energies are high and the
distance between the optical fiber tip and surgical target is small
or the fiber is in contact with the surgical target, the vast
majority of the surgical energy arrives at the stone, at least for
the first pulse. In real world surgery, however, the surgical
targets irregular and often in violent motion, agitated by the
expansion and collapse of vapor bubbles, making intimate contact
between the fiber tip and the target impossible to maintain.
[0023] The infrared output of continuous wave (CW) surgical lasers
used for soft tissue ablation and resection is similarly absorbed,
but being CW, the absorption is incomplete at surgical powers.
While incomplete, energy loss to absorption by water is sufficient
to cause problems. A continuous stream of bubbles may obscure clear
visualization of the surgical site under treatment and in order to
maintain surgical efficacy, fibers are maintained in contact, or
very near contact, with soft tissues to the disadvantage of fiber
lifetime and performance.
[0024] First principles of optics and physical chemistry may be
used to approximate the energy loss due to vapor bubble formation.
Where the radiant intensity is as high as possible--with energy
delivered via the smallest diameter, least divergent optical fibers
that are compatible with cleared surgical lasers (0.2 mm core,
12.7.degree. half angle divergence, assuming mode filled
condition)--the volume of water interacting with the laser
pulse/beam, between the fiber exit surface and the kidney stone, is
approximated by a frustoconical solid FIG. 2 with volume V given
by
V = .pi. h 3 ( r 1 2 + r 1 r 2 + r 2 2 ) , ##EQU00001##
where h is the fiber tip to target distance, r.sub.1 is half the
diameter 75 and r.sub.2 is half the diameter 45 and where
r.sub.1=[r.sub.2+2 (tan 12.7)]/2. For h=1.0 mm separation and a 0.2
mm core 40 fiber, r.sub.1=0.325 mm, r.sub.2=0.1 mm so V=0.155
mm.sup.2.
[0025] Assuming the temperature of the water is normal biological
temperature (37.degree. C.) and approximating the density of water
at 1 gram (g) per cm.sup.3 for 0.000155 g of water in the conical
frustum, given a heat of vaporization of 2257 J/g and approximating
the specific heat of water for the relevant temperature range of
37.degree. C. to 100.degree. C. at 4.187 J/.degree. C., we arrive
at approximately 0.39 J required to vaporize the "Moses volume".
The larger the fiber diameter, the larger the Moses volume and the
greater the energy required to vaporize the path to the stone. The
fluid dynamics and thermal gradients within the surgical field are
admittedly ignored in this approximation, but practice proves the
approximation valid; in that 0.2 mm is the smallest commonly
available fiber core diameter, the lowest two settings for most
holmium lasers, 0.2 J and 0.4 J, prove ineffective at 1 mm or
greater fiber tip to target distances.
[0026] U.S. Pat. No. 9,895,196 teaches provision of two laser
pulses, a first pulse optimized to open a vapor pathway based upon
the fiber tip to target separation, followed by a second pulse that
is timed to pass just as the Moses bubble is beginning to collapse
such that the retropulsion of the target caused by the expansion of
the bubble is revered in its collapse. While this strategy has
theoretical value, it is impractical to precisely measure fiber tip
to target distance for each and every pulse to be delivered in
laser lithotripsy for optimization of each Moses bubble; fiber
position is under manual control, fiber tips degrade, stone
surfaces are irregular and stones dance about, often violently,
while ablating and fragmenting. It would be simpler to simply
provide a highly absorbed, continuous wave (CW) signal to maintain
a "Moses corridor" between the fiber and target for delivery of
unimpeded surgical pulses.
[0027] A first embodiment of an improved surgical laser system is
comprised of a standard, high pulse energy, flashlamp or diode
pumped, solid state gain medium combined with a low power, diode or
DPSS laser with continuous emission at or adjacent the peak
absorptivity of water at .about.1930 nm, and optically coupled to a
fiber optic laser energy delivery device. The combination of the
two lasers may be accomplished via a crystalline beam combiner,
rotating mirrors or other means known in the art.
[0028] The power of the diode laser is selected to be sufficient to
establish and maintain a vapor bubble between the fiber delivery
device output tip and the surgical target ("gap"). This vapor
bubble need not bridge the entire gap, but may fall short in some
cases where the gap varies considerably with time, yet should be
sufficient to substantially reduce the chaotic bubble
formation/collapse cycle generally seen in pulse infrared laser
surgery.
[0029] Ideally the divergence of the CW beam is greater than the
divergence of the therapeutic pulses. Optical fiber constructions
FIG. 2 used in laser lithotripsy offer a convenient means of
ensuring such. The low [OH] synthetic fused silica core 40 is clad
50 with fluorine-doped, low [OH] fused silica having a slightly
lower refractive index than the core 40 material. Therapeutic laser
pulses are contained within the core:cladding waveguide thus
provided. At the long wavelengths and high peak pulse energies used
in laser lithotripsy, however, some substantial evanescence
typically extends beyond the glass cladding, sufficient to heat the
fiber buffer 70 to beyond its glass transition temperature and, in
some cases, melt or burn the buffer. A secondary containment is
therefore provided in the form of a polymer cladding 60 with a
refractive index lower than the glass cladding 50.
[0030] The polymer cladding produces a second fiber numerical
aperture (NA) here higher off axis light rays may be propagated.
The efficiency of propagation within the higher (or secondary) NA
is a function of absorption and scatter of light within the core
40, the fluorine-doped glass cladding 50 and, to some degree, the
polymer cladding 60. The polymers used, e.g. optical silicones,
fluoroacrylates, fluorourethances, generally absorb and scatter
long wavelength light more than glasses: the longer the wavelength,
the more absorption and scatter.
[0031] As may be seen in FIG. 3, holmium wavelengths, e.g. 2140 nm
80, nudge up against the longest practical wavelength that can
safely be delivered by All Fused Silica (AFS) optical fiber, under
high peak power and in tortuous paths. Thulium laser wavelengths 85
are shorter and present far less of a challenge to the fiber
construction due to much lower peak powers produced in CW lasers.
The CW Moses corridor producing laser at 1930 nm 90 is an even
shorter wavelength than thulium and the power required to open and
maintain the Moses corridor is substantially lower than that
required at thulium's wavelength, principally due to the almost
2-fold larger specific absorption coefficient for water at 1930 nm
10 versus thulium at 2000 nm 20 FIG. 1. The 1930 nm laser may
accordingly be carried within the secondary NA of the fiber 95,
with a numerical aperture equivalent to polymer clad or Hard
Polymer Clad (HPC) fiber, such that divergence of the Moses
corridor maintaining beam is higher than the therapeutic pulse
divergence.
[0032] Holmium laser energy is poorly contained by Hard Polymer
Cladding (and other common organic cladding materials) 105 due to
relatively strong interaction of the wavelengths with the polymers
and high peak pulse powers. HPC fiber coatings contain thulium
laser energy 100 better than holmium laser energy 105 albeit poorly
due to the high powers typically used in surgery. The power of the
Moses corridor laser, however, is considerably lower than that
required for surgery, such that even relatively significant
interaction with the HPC coating 95 does not risk overheating the
fiber.
[0033] It is therefore critical to contain surgical wavelengths to
the primary NA to avoid overheating the fiber coatings (polymer
cladding and buffer) that leads to a catastrophic failure mode
known as "burn through" in the surgical art. Surgical energy is
launched into the primary NA with maximum angles below the maximum
acceptance angle (approximately 12.5.degree. off the longitudinal
axis for a 0.22 primary NA), resulting in a semi-Gaussian output
beam profile FIG. 4A where the fiber is relaxed (not under
significant bending stress). Where surgical access requires the
fiber to traverse a tortuous path, as is typical in laser URS
(Ureteroscopy), output beam profiles become more flattened FIG. 4B
with laser energy carried relatively evenly throughout the primary
NA. Bending beyond the optical bend limit minimum causes some
surgical energy to leak into the secondary NA at angles beyond the
primary NA containment capacity.
[0034] Ideally, the Moses corridor maintaining beam is carried
and/or delivered as an annular beam rather than a cylindrical
solid. An annulus is all that is required to maintain the Moses
corridor once it has been established, either by duration of
interaction with the aqueous environment or by passage of the first
therapeutic laser pulse. An annular beam may be established by skew
launch into the fiber, optical conditioning and other means known
in the art, such as off axis launch FIG. 4C. In that the Moses
corridor maintaining CW laser power is very low compared to the
surgical laser power, the power loss to absorption in the polymer
cladding remains well below the failure threshold, even where the
annular character of propagation is enhanced in bending stress
during surgery.
[0035] Herewith, another embodiment is a surgical method that
includes establishing a steam bubble between a fiber tip and a
surgical target; maintaining the steam bubble by providing a
low-power, continuous-wave laser emission; and then delivering to
the surgical target through the steam bubble a therapeutic laser
emission providing ablation of the surgical target. Notably, this
method reduces or eliminates any therapeutic laser power lost to
the formation of a bubble between the fiber tip and the surgical
target. Preferably, greater than 90%, 92%, 94%, 96%, 98%, 99%,
99.5%, or 99.9% of the power output from the therapeutic laser
emission reaches the surgical target. More preferably, no
therapeutic laser emission power is lost by absorption of water
between the fiber tip and the surgical target.
[0036] Herein, the steam bubble is preferably maintained by laser
emissions from the fiber tip, the laser being a low-power,
continuous-wave laser that is, generally, considered to be of no
therapeutic use. Notably, the term low-power means that the
continuous-wave laser (and the CW laser emissions) have
insufficient power to ablate a surgical target; more preferably,
low-power means that the CW laser and emissions have insufficient
power to affect a physiochemical change in the surgical target; for
example, insufficient power to cauterize, ablate, facilitate a
Malliard reaction, denature proteins, or cause the pulverization or
the disunification by impact (implosion) of the surgical target.
Importantly when used in laser lithotripsy, the low-power means
that the CW laser and emissions fail to cause cavitation effects
and fail to lead to stone/calculi destruction. Notably, a low-power
CW laser (and emissions) provide no "plasma bubble" or similar
cavitation that is believed to lead to ablation effects.
[0037] Preferably, the CW laser and emissions are of sufficient
power to vaporize or maintain the vaporization of water at the
fiber tip. In one example, the continuous-wave laser emission has a
power output of less than 5 Watts, less than 2 W, less than 1 W,
less than 0.5 W, less than 0.4 W, less than 0.3 W, less than 0.25
W, or less than 0.2 W. Accordingly, it is preferred that the
continuous-wave laser emission has a power output that is
insufficient to affect ablation of the surgical target, preferably
insufficient to affect a change in the surgical target. In one
instance, the continuous-wave laser emission has a power output
that is sufficient to dehydrate the surgical target.
[0038] In one instance, the continuous-wave laser emission has a
divergent emission from the fiber tip. In another instance, the
continuous-wave laser emission has an annular beam profile. In
still another instance, the continuous-wave laser emission has a
beam profile that does not significantly overlap with the beam
profile of the therapeutic laser emission (e.g., overlap is less
than 20%, 15%, 10%, 5%).
[0039] In one particularly preferably instance, the continuous-wave
laser emission has an emissions wavelength of about 1930 nm.
Herein, the emissions wavelength can be 1930 nm.+-.30 nm, .+-.20
nm, or .+-.10 nm.
[0040] Herein, the continuous-wave laser emission is provided by
one or more laser diodes or diode-pumped solid-state lasers coupled
to the fiber tip. That is, the continuous-wave laser emission is
that of a CW laser diode or diodes, or a diode-pumped solid-state
laser.
[0041] In another instance, the ablation of the surgical target is
provided by therapeutic laser emissions from the fiber tip, this
laser being a high-power, pulsed laser that is commonly found in
therapeutic use (e.g., a holmium laser or a thulium laser). In one
example, the therapeutic laser emission has a wavelength greater
than 1960 nm, 1970 nm, 1980 nm, 1990 nm, or 2000 nm. Specific
wavelengths can be those provided by, for example, a holmium laser,
a thulium laser, or another high wavelength surgical laser. In
another example, the therapeutic laser emission has a power output
of greater than 5 Watts, 10 W, 25 W, 50 W, or 100 W.
[0042] Preferably, the therapeutic laser emission is delivered as a
plurality of laser pulses. In one instance, the plurality of laser
pulses is at about 5 Hz, 10 Hz, 15 Hz, 20 Hz, 25 Hz, 30 Hz, 35 Hz,
40 Hz, 45 Hz, 50 Hz, 55 Hz or 60 Hz; in another instance, the
plurality of laser pulses is provided between about 10 Hz and about
2 KHz.
[0043] Herein, the term ablation means the fragmentation,
disintegration, abscission, violent expansion of a hard surgical
target (e.g., urinary, biliary, or salivary calculi) and/or the
vaporization, excision, incision of a soft surgical target.
Notably, the term ablation does not include the pulverization or
the disunification by impact (implosion) of a surgical target by
applying a shock wave to the target surface. In one instance, the
ablation of the surgical target is provided by the rapid expansion
of water within the surgical target. Accordingly, the surgical
target is preferably porous and/or hydrated--containing sufficient
water to facilitate the ablation (e.g., in the pores of the
surgical target). More preferably, the surgical target is not
dehydrated (e.g., dry) or sufficiently non-porous that the target
retains little to no water. In another instance, the ablation of
the surgical target includes the rapid expansion and contraction of
water within the surgical target. These rapid changes within the
surgical target, preferably, cause the disintegrating the surgical
target (e.g., causing the surgical target to fracture and powder),
preferably resulting in a fine powder that is carried from the
surgical site (the location of the surgical target) by a water
lavage.
[0044] In another instance, the therapeutic laser emission can be
delivered at a wavelength that is less than 500 nm. In this
instance, it is preferable that the surgical target is vaporized
instead of disintegrated. Notably, at below 500 nm, the
wavelength(s) are preferably chosen to be one or more endogenic
chromophores (e.g., oxy- or deoxy-hemoglobin). In one example, the
therapeutic laser emission is a combination of a plurality of
emissions each having a wavelength less than 500 nm, preferably
chosen to be one or more endogenic chromophores, degradation
products, or thermal product.
[0045] Notably, the method describe herein is useful in
orthoscopic, lithotripsic, or similar laser surgical procedure, but
open, percutaneous or endoscopic access. Accordingly, the
continuous-wave laser emission and the therapeutic laser emission
are provided via an optical fiber. Preferably, the optical fiber
has a fused silica core, the fused silica core clad with a fluorine
doped silica cladding, the fluorine doped silica cladding having a
polymer cladding; wherein the therapeutic laser emission is
contained within the fused silica core by the fluorine doped silica
cladding. In one particularly preferable instance, the
continuous-wave laser emission is contained within the fluorine
doped silica cladding by the polymer cladding. Notably, the process
can include providing the CW laser emission to the optical fiber
(from the CW laser) with a high launch angle, that is, along a path
that is not commensurate with the fiber's longitudinal axis. In one
instance, the continuous-wave laser emission it provided to the
optical fiber with a high angle launch that is greater than about
4.degree., about 8.degree., about 10.degree., about 12.5.degree.,
or about 15.degree. off the fiber longitudinal axis.
[0046] FIG. 5 illustrates the off-axis launch of the CW Moses
corridor producing beam 110 with respect to the on-axis launch of
the therapeutic, pulsed beam 115 according to embodiments
disclosed. The CW beam 110 is focused by a lens 120 or lenses as is
the pulsed beam 115 at 125, producing a converging CW beam 130 and
converging pulsed beam 135, both imparting the fiber input aperture
140 but where the pulsed beam 115 is centrosymmetric about the
fiber longitudinal axis and the CW beam 110 is not. The pulsed
energy is contained within the fiber core 145 as meridional and
skew rays where the CW beam may be contained within the core 145 as
skew rays, or the predominantly within the glass cladding 150 as
skew rays, dependent upon the off-axis angle 175 of the CW launch
and the refractive indices of the core 145, glass cladding 150 and
the polymer cladding 155. A buffer coating 160 is depicted for
completeness.
[0047] Launching the CW, Moses corridor beam 110/130 is skew rays
produces a predominantly annular output beam 170 (FIG. 4C) upon
exiting the fiber delivery aperture 165 whereas launching the
pulsed, therapeutic beam 115/125 on the fiber axis produces a
semi-Gaussian FIG. 4A or essentially top-hat FIG. 4B beam upon
exiting the fiber delivery aperture 165.
[0048] An important feature of the current method is the formation
or establishment of the stream bubble between the fiber tip and the
surgical target. Notably, the stream bubble can be established by
providing the continuous-wave laser emission and/or the therapeutic
laser emission to water positioned between the fiber tip and the
surgical target. In instances wherein the CW laser emission is
insufficient to generate a stream bubble of sufficient size, the CW
laser and the therapeutic laser can be used in tandem.
Alternatively, the steam bubble can be established by a pulse of
the therapeutic laser and then maintained by the CW laser. A
variable length or power pulse of the therapeutic laser. Examples
of variable length and power pulses are known in the art for the
generation of steam bubbles prior to the firing of (fully strength)
therapeutic pulses.
[0049] Notably, the evaporation of the water between the fiber tip
and the surgical target requires sufficient power. While the total
power necessary is based on the distance between the fiber tip and
the surgical target as well as the fiber diameter; generally, the
steam bubble can be established by providing a power output of
greater than 1 Watt, 2 Watts, 3 Watts, 4 Watts, 5 Watts, 6 Watts, 7
Watts, 8 Watts, 9 Watts, or 10 Watts.
[0050] In one instance where the continuous-wave laser emission has
an annular beam profile, the steam bubble is established by
therapeutic laser emission. Notably, if the annular beam profile of
the CW laser emission is sufficiently broad, this emission would
leave an un-vaporized portion of water between the fiber tip and
the surgical target, in such a circumstance, it is preferably to
utilize a therapeutic pulse or a therapeutic pulse with the CW
emissions to generate the steam bubble. That is, establishing the
steam bubble can include providing the continuous-wave laser
emission and the therapeutic laser emission, whereby the
therapeutic laser emission eliminates residual water between the
fiber tip and the surgical target, and whereby the continuous-wave
laser emission maintains the steam bubble.
[0051] In another instance, the volume and number of stream bubbles
is relatively constant during the surgical process. In one example,
the volume of the steam bubble stays relatively constant throughout
the ablation of the surgical target. Preferably, the volume of the
steam bubble changes less than 50 vol. %, less than 40 vol. %, less
than 30 vol. %, less than 25 vol. %, less than 20 vol. %, less than
15 vol. %, less than 10 vol. % while delivering the therapeutic
laser emission to the surgical target. Accordingly, there is not a
large displacement of material (e.g., water) while delivering the
therapeutic laser emission. In one instance, this relatively
constant volume reduces retropulsion or the repulsion of the
surgical target during application of the therapeutic laser
emission. While some retropulsion may occur due to the ablation of
the surgical target, preferably, any retropulsion caused by the
formation and collapse of bubbles between the fiber tip and the
surgical target are eliminated. That is, eliminated by the
maintenance of a single steam bubble between the fiber tip and the
surgical target.
[0052] Preferably, the steam bubble is adjacent to the surgical
target. That is, the steam bubble preferably occupies the volume
between the fiber tip and the surgical target and thereby provides
a gaseous beam path for the therapeutic laser. In instances,
wherein the steam bubble is not adjacent to the surgical target but
is proximal thereto, the therapeutic laser emission preferably
eliminates any residual water between the steam bubble and the
surgical target. Preferably, once the therapeutic laser emission
eliminates the residual water the CW laser emission maintains the
steam bubble from the fiber tip to the surgical target. In such an
example, the therapeutic laser emission can have a power output of
greater than 10 W, 25 W, 50 W, or 100 W at the fiber tip and the
maintenance of the steam bubble by the CW laser emission prevents a
reduction of the power output between the fiber tip and the
surgical target. In instances wherein the CW laser is insufficient
to maintain the steam bubble for the full distance from the fiber
tip to the surgical target, the steam bubble prevents a large
reduction of power and prevents or reduces the retropulsion of the
surgical target. More preferably, when the CW laser permits a small
portion of water to contact the surface of the surgical target, the
interaction of this surface water with the therapeutic laser
emission aids in the ablation of the surgical target and/or aids in
the cleaning of the surgical target surface during ablation.
[0053] Another instance is a surgical device that includes a
therapeutic laser emission source having a power output of greater
than 10 Watts, 25 Watts, 50 Watts, or 100 Watts; and a
continuous-wave laser emission source having a power output of less
than 5 Watts, less than 2 Watts, less than 1 Watt, less than 0.5
Watts, or less than 0.2 Watts. The surgical device further includes
a low-angle therapeutic laser emission launch adapted to provide a
therapeutic laser emission to a core of an optical fiber with a
launch angle of less than about 4.degree., 3.degree., 2.degree., or
1.degree.; and a high-angle continuous-wave laser emission launch
adapted to provide a continuous-wave laser emission to the optical
fiber with a launch angle of greater than about 4.degree.,
8.degree., 12.degree., or 15.degree.. That is, the therapeutic
laser and the CW laser are provided to the fiber with different
launch angles. Notably, the low-angle and high-angle of the
respective launches are with respect to a longitudinal axis of the
optical fiber.
[0054] Preferably, the surgical device includes an optical fiber
having a fused silica core, the fused silica core clad with a
fluorine doped silica cladding, the fluorine doped silica cladding
having a polymer cladding.
[0055] In one instance, the surgical device includes a holmium
laser or a thulium laser as the therapeutic laser emission source.
In another instance, the continuous-wave laser emission source is
one or more laser diodes or diode-pumped solid-state lasers, the
emission source having an emissions wavelength of 1930.+-.30 nm,
.+-.20 nm, or .+-.10 nm.
[0056] Another benefit of using a low power, CW laser for
maintenance of the Moses Corridor as opposed to using the
therapeutic laser wavelength is a reduction in thermal stress on
surrounding tissues that are in contact with the surgical irrigant.
Essentially all of the laser energy delivered to a kidney stone
results in the heating of the water, some directly in forming the
Moses vapor bubble, and the rest indirectly by heating the kidney
stone which transfers that heat to the water my various thermal
mechanisms. The time scale of transfer is irrelevant in surgical
treatment timeframes that range from a dozen seconds to over a
minute of continuous lasing. What differs is the fraction of the
total energy that produces therapeutic benefit.
[0057] The length of time a surgeon will continuously activate the
laser is largely dependent upon the results observed. If little
material is removed with each pulse, lasing intervals tend to be
long as the surgeon concentrates the laser energy upon the stone
mass. Where the stone is moving--away from the fiber or dancing
about in what is known in the art as "popcorn" motion--only random
pulses may have therapeutic effect. Minimization of motion enhances
surgical efficacy for a given amount of power applied. The lower
the amount of total energy required performing a procedure, the
less the chance of the patient's surrounding tissue suffers
inadvertent thermal damage.
[0058] A 0.242 mm core optical fiber delivering 1 J pulses at 40 Hz
can raise the temperature of the surgical irrigant to over
70.degree. C. within one minute, beyond the denaturing temperature
of most proteins; as more powerful lasers are approved for surgical
use, the risk of patient injury due to thermal damage to tissues
increases. A 0.2 mm fiber, at 1 mm separation between fiber tip and
stone, wastes almost 40% of a 1 J pulse in heating the surgical
irrigant, or almost 16 W at 40 Hz: the larger the fiber, the
greater the inefficiency. The invention described herein may
maintain a Moses Corridor with less than 5 watts, at any power
setting and for any size fiber.
[0059] While the compositions and methods of this invention have
been described in terms of preferred embodiments, it will be
apparent to those of skill in the art that variations may be
applied to the compositions and/or methods in the steps or in the
sequence of steps of the method described herein without departing
from the concept, spirit and scope of the invention. More
specifically, it will be apparent that certain agents that are both
chemically and physically related may be substituted for the agents
described herein while the same or similar results would be
achieved. All such similar substitutes and modifications apparent
to those skilled in the art are deemed to be within the spirit,
scope and concept of the invention as defined by the appended
claims.
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